/src/openssl/crypto/ec/curve448/eddsa.c

Source (jump to first uncovered line)
/*
 * Copyright 2017-2024 The OpenSSL Project Authors. All Rights Reserved.
 * Copyright 2015-2016 Cryptography Research, Inc.
 *
 * Licensed under the Apache License 2.0 (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 *
 * Originally written by Mike Hamburg
 */
#include <string.h>
#include <openssl/crypto.h>
#include <openssl/evp.h>
#include "crypto/ecx.h"
#include "curve448_local.h"
#include "word.h"
#include "ed448.h"
#include "internal/numbers.h"

#define COFACTOR 4

static c448_error_t oneshot_hash(OSSL_LIB_CTX *ctx, uint8_t *out, size_t outlen,
                                 const uint8_t *in, size_t inlen,
                                 const char *propq)
{
    EVP_MD_CTX *hashctx = EVP_MD_CTX_new();
    EVP_MD *shake256 = NULL;
    c448_error_t ret = C448_FAILURE;

    if (hashctx == NULL)
        return C448_FAILURE;

    shake256 = EVP_MD_fetch(ctx, "SHAKE256", propq);
    if (shake256 == NULL)
        goto err;

    if (!EVP_DigestInit_ex(hashctx, shake256, NULL)
            || !EVP_DigestUpdate(hashctx, in, inlen)
            || !EVP_DigestFinalXOF(hashctx, out, outlen))
        goto err;

    ret = C448_SUCCESS;
 err:
    EVP_MD_CTX_free(hashctx);
    EVP_MD_free(shake256);
    return ret;
}

static void clamp(uint8_t secret_scalar_ser[EDDSA_448_PRIVATE_BYTES])
{
    secret_scalar_ser[0] &= -COFACTOR;
    secret_scalar_ser[EDDSA_448_PRIVATE_BYTES - 1] = 0;
    secret_scalar_ser[EDDSA_448_PRIVATE_BYTES - 2] |= 0x80;
}

static c448_error_t hash_init_with_dom(OSSL_LIB_CTX *ctx, EVP_MD_CTX *hashctx,
                                       uint8_t prehashed,
                                       uint8_t for_prehash,
                                       const uint8_t *context,
                                       size_t context_len,
                                       const char *propq)
{
    /* ASCII: "SigEd448", in hex for EBCDIC compatibility */
    const char dom_s[] = "\x53\x69\x67\x45\x64\x34\x34\x38";
    uint8_t dom[2];
    EVP_MD *shake256 = NULL;

    if (context_len > UINT8_MAX)
        return C448_FAILURE;

    dom[0] = (uint8_t)(2 - (prehashed == 0 ? 1 : 0)
                       - (for_prehash == 0 ? 1 : 0));
    dom[1] = (uint8_t)context_len;

    shake256 = EVP_MD_fetch(ctx, "SHAKE256", propq);
    if (shake256 == NULL)
        return C448_FAILURE;

    if (!EVP_DigestInit_ex(hashctx, shake256, NULL)
            || !EVP_DigestUpdate(hashctx, dom_s, sizeof(dom_s)-1)
            || !EVP_DigestUpdate(hashctx, dom, sizeof(dom))
            || !EVP_DigestUpdate(hashctx, context, context_len)) {
        EVP_MD_free(shake256);
        return C448_FAILURE;
    }

    EVP_MD_free(shake256);
    return C448_SUCCESS;
}

/* In this file because it uses the hash */
c448_error_t
ossl_c448_ed448_convert_private_key_to_x448(
                            OSSL_LIB_CTX *ctx,
                            uint8_t x[X448_PRIVATE_BYTES],
                            const uint8_t ed [EDDSA_448_PRIVATE_BYTES],
                            const char *propq)
{
    /* pass the private key through oneshot_hash function */
    /* and keep the first X448_PRIVATE_BYTES bytes */
    return oneshot_hash(ctx, x, X448_PRIVATE_BYTES, ed,
                        EDDSA_448_PRIVATE_BYTES, propq);
}

c448_error_t
ossl_c448_ed448_derive_public_key(
                        OSSL_LIB_CTX *ctx,
                        uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
                        const uint8_t privkey[EDDSA_448_PRIVATE_BYTES],
                        const char *propq)
{
    /* only this much used for keygen */
    uint8_t secret_scalar_ser[EDDSA_448_PRIVATE_BYTES];
    curve448_scalar_t secret_scalar;
    unsigned int c;
    curve448_point_t p;

    if (!oneshot_hash(ctx, secret_scalar_ser, sizeof(secret_scalar_ser),
                      privkey,
                      EDDSA_448_PRIVATE_BYTES,
                      propq))
        return C448_FAILURE;

    clamp(secret_scalar_ser);

    ossl_curve448_scalar_decode_long(secret_scalar, secret_scalar_ser,
                                     sizeof(secret_scalar_ser));

    /*
     * Since we are going to mul_by_cofactor during encoding, divide by it
     * here. However, the EdDSA base point is not the same as the decaf base
     * point if the sigma isogeny is in use: the EdDSA base point is on
     * Etwist_d/(1-d) and the decaf base point is on Etwist_d, and when
     * converted it effectively picks up a factor of 2 from the isogenies.  So
     * we might start at 2 instead of 1.
     */
    for (c = 1; c < C448_EDDSA_ENCODE_RATIO; c <<= 1)
        ossl_curve448_scalar_halve(secret_scalar, secret_scalar);

    ossl_curve448_precomputed_scalarmul(p, ossl_curve448_precomputed_base,
                                        secret_scalar);

    ossl_curve448_point_mul_by_ratio_and_encode_like_eddsa(pubkey, p);

    /* Cleanup */
    ossl_curve448_scalar_destroy(secret_scalar);
    ossl_curve448_point_destroy(p);
    OPENSSL_cleanse(secret_scalar_ser, sizeof(secret_scalar_ser));

    return C448_SUCCESS;
}

c448_error_t
ossl_c448_ed448_sign(OSSL_LIB_CTX *ctx,
                     uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
                     const uint8_t privkey[EDDSA_448_PRIVATE_BYTES],
                     const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
                     const uint8_t *message, size_t message_len,
                     uint8_t prehashed, const uint8_t *context,
                     size_t context_len, const char *propq)
{
    curve448_scalar_t secret_scalar;
    EVP_MD_CTX *hashctx = EVP_MD_CTX_new();
    c448_error_t ret = C448_FAILURE;
    curve448_scalar_t nonce_scalar;
    uint8_t nonce_point[EDDSA_448_PUBLIC_BYTES] = { 0 };
    unsigned int c;
    curve448_scalar_t challenge_scalar;

    if (hashctx == NULL)
        return C448_FAILURE;

    {
        /*
         * Schedule the secret key, First EDDSA_448_PRIVATE_BYTES is serialized
         * secret scalar,next EDDSA_448_PRIVATE_BYTES bytes is the seed.
         */
        uint8_t expanded[EDDSA_448_PRIVATE_BYTES * 2];

        if (!oneshot_hash(ctx, expanded, sizeof(expanded), privkey,
                          EDDSA_448_PRIVATE_BYTES, propq))
            goto err;
        clamp(expanded);
        ossl_curve448_scalar_decode_long(secret_scalar, expanded,
                                         EDDSA_448_PRIVATE_BYTES);

        /* Hash to create the nonce */
        if (!hash_init_with_dom(ctx, hashctx, prehashed, 0, context,
                                context_len, propq)
                || !EVP_DigestUpdate(hashctx,
                                     expanded + EDDSA_448_PRIVATE_BYTES,
                                     EDDSA_448_PRIVATE_BYTES)
                || !EVP_DigestUpdate(hashctx, message, message_len)) {
            OPENSSL_cleanse(expanded, sizeof(expanded));
            goto err;
        }
        OPENSSL_cleanse(expanded, sizeof(expanded));
    }

    /* Decode the nonce */
    {
        uint8_t nonce[2 * EDDSA_448_PRIVATE_BYTES];

        if (!EVP_DigestFinalXOF(hashctx, nonce, sizeof(nonce)))
            goto err;
        ossl_curve448_scalar_decode_long(nonce_scalar, nonce, sizeof(nonce));
        OPENSSL_cleanse(nonce, sizeof(nonce));
    }

    {
        /* Scalarmul to create the nonce-point */
        curve448_scalar_t nonce_scalar_2;
        curve448_point_t p;

        ossl_curve448_scalar_halve(nonce_scalar_2, nonce_scalar);
        for (c = 2; c < C448_EDDSA_ENCODE_RATIO; c <<= 1)
            ossl_curve448_scalar_halve(nonce_scalar_2, nonce_scalar_2);

        ossl_curve448_precomputed_scalarmul(p, ossl_curve448_precomputed_base,
                                            nonce_scalar_2);
        ossl_curve448_point_mul_by_ratio_and_encode_like_eddsa(nonce_point, p);
        ossl_curve448_point_destroy(p);
        ossl_curve448_scalar_destroy(nonce_scalar_2);
    }

    {
        uint8_t challenge[2 * EDDSA_448_PRIVATE_BYTES];

        /* Compute the challenge */
        if (!hash_init_with_dom(ctx, hashctx, prehashed, 0, context, context_len,
                                propq)
                || !EVP_DigestUpdate(hashctx, nonce_point, sizeof(nonce_point))
                || !EVP_DigestUpdate(hashctx, pubkey, EDDSA_448_PUBLIC_BYTES)
                || !EVP_DigestUpdate(hashctx, message, message_len)
                || !EVP_DigestFinalXOF(hashctx, challenge, sizeof(challenge)))
            goto err;

        ossl_curve448_scalar_decode_long(challenge_scalar, challenge,
                                         sizeof(challenge));
        OPENSSL_cleanse(challenge, sizeof(challenge));
    }

    ossl_curve448_scalar_mul(challenge_scalar, challenge_scalar, secret_scalar);
    ossl_curve448_scalar_add(challenge_scalar, challenge_scalar, nonce_scalar);

    OPENSSL_cleanse(signature, EDDSA_448_SIGNATURE_BYTES);
    memcpy(signature, nonce_point, sizeof(nonce_point));
    ossl_curve448_scalar_encode(&signature[EDDSA_448_PUBLIC_BYTES],
                                challenge_scalar);

    ossl_curve448_scalar_destroy(secret_scalar);
    ossl_curve448_scalar_destroy(nonce_scalar);
    ossl_curve448_scalar_destroy(challenge_scalar);

    ret = C448_SUCCESS;
 err:
    EVP_MD_CTX_free(hashctx);
    return ret;
}

c448_error_t
ossl_c448_ed448_sign_prehash(
                        OSSL_LIB_CTX *ctx,
                        uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
                        const uint8_t privkey[EDDSA_448_PRIVATE_BYTES],
                        const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
                        const uint8_t hash[64], const uint8_t *context,
                        size_t context_len, const char *propq)
{
    return ossl_c448_ed448_sign(ctx, signature, privkey, pubkey, hash, 64, 1,
                                context, context_len, propq);
}

static c448_error_t
c448_ed448_pubkey_verify(const uint8_t *pub, size_t pub_len)
{
    curve448_point_t pk_point;

    if (pub_len != EDDSA_448_PUBLIC_BYTES)
        return C448_FAILURE;

    return ossl_curve448_point_decode_like_eddsa_and_mul_by_ratio(pk_point, pub);
}

c448_error_t
ossl_c448_ed448_verify(
                    OSSL_LIB_CTX *ctx,
                    const uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
                    const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
                    const uint8_t *message, size_t message_len,
                    uint8_t prehashed, const uint8_t *context,
                    uint8_t context_len, const char *propq)
{
    curve448_point_t pk_point, r_point;
    c448_error_t error;
    curve448_scalar_t challenge_scalar;
    curve448_scalar_t response_scalar;
    /* Order in little endian format */
    static const uint8_t order[] = {
        0xF3, 0x44, 0x58, 0xAB, 0x92, 0xC2, 0x78, 0x23, 0x55, 0x8F, 0xC5, 0x8D,
        0x72, 0xC2, 0x6C, 0x21, 0x90, 0x36, 0xD6, 0xAE, 0x49, 0xDB, 0x4E, 0xC4,
        0xE9, 0x23, 0xCA, 0x7C, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
        0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
        0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x3F, 0x00
    };
    int i;

    /*
     * Check that s (second 57 bytes of the sig) is less than the order. Both
     * s and the order are in little-endian format. This can be done in
     * variable time, since if this is not the case the signature if publicly
     * invalid.
     */
    for (i = EDDSA_448_PUBLIC_BYTES - 1; i >= 0; i--) {
        if (signature[i + EDDSA_448_PUBLIC_BYTES] > order[i])
            return C448_FAILURE;
        if (signature[i + EDDSA_448_PUBLIC_BYTES] < order[i])
            break;
    }
    if (i < 0)
        return C448_FAILURE;

    error =
        ossl_curve448_point_decode_like_eddsa_and_mul_by_ratio(pk_point, pubkey);

    if (C448_SUCCESS != error)
        return error;

    error =
        ossl_curve448_point_decode_like_eddsa_and_mul_by_ratio(r_point, signature);
    if (C448_SUCCESS != error)
        return error;

    {
        /* Compute the challenge */
        EVP_MD_CTX *hashctx = EVP_MD_CTX_new();
        uint8_t challenge[2 * EDDSA_448_PRIVATE_BYTES];

        if (hashctx == NULL
                || !hash_init_with_dom(ctx, hashctx, prehashed, 0, context,
                                       context_len, propq)
                || !EVP_DigestUpdate(hashctx, signature, EDDSA_448_PUBLIC_BYTES)
                || !EVP_DigestUpdate(hashctx, pubkey, EDDSA_448_PUBLIC_BYTES)
                || !EVP_DigestUpdate(hashctx, message, message_len)
                || !EVP_DigestFinalXOF(hashctx, challenge, sizeof(challenge))) {
            EVP_MD_CTX_free(hashctx);
            return C448_FAILURE;
        }

        EVP_MD_CTX_free(hashctx);
        ossl_curve448_scalar_decode_long(challenge_scalar, challenge,
                                         sizeof(challenge));
        OPENSSL_cleanse(challenge, sizeof(challenge));
    }
    ossl_curve448_scalar_sub(challenge_scalar, ossl_curve448_scalar_zero,
                             challenge_scalar);

    ossl_curve448_scalar_decode_long(response_scalar,
                                     &signature[EDDSA_448_PUBLIC_BYTES],
                                     EDDSA_448_PRIVATE_BYTES);

    /* pk_point = -c(x(P)) + (cx + k)G = kG */
    ossl_curve448_base_double_scalarmul_non_secret(pk_point,
                                                   response_scalar,
                                                   pk_point, challenge_scalar);
    return c448_succeed_if(ossl_curve448_point_eq(pk_point, r_point));
}

c448_error_t
ossl_c448_ed448_verify_prehash(
                    OSSL_LIB_CTX *ctx,
                    const uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
                    const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
                    const uint8_t hash[64], const uint8_t *context,
                    uint8_t context_len, const char *propq)
{
    return ossl_c448_ed448_verify(ctx, signature, pubkey, hash, 64, 1, context,
                                  context_len, propq);
}

int
ossl_ed448_sign(OSSL_LIB_CTX *ctx, uint8_t *out_sig,
                const uint8_t *message, size_t message_len,
                const uint8_t public_key[57], const uint8_t private_key[57],
                const uint8_t *context, size_t context_len,
                const uint8_t phflag, const char *propq)
{
    return ossl_c448_ed448_sign(ctx, out_sig, private_key, public_key, message,
                                message_len, phflag, context, context_len,
                                propq) == C448_SUCCESS;
}

/*
 * This function should not be necessary since ossl_ed448_verify() already
 * does this check internally.
 * For some reason the FIPS ACVP requires a EDDSA KeyVer test.
 */
int
ossl_ed448_pubkey_verify(const uint8_t *pub, size_t pub_len)
{
    return c448_ed448_pubkey_verify(pub, pub_len);
}

int
ossl_ed448_verify(OSSL_LIB_CTX *ctx,
                  const uint8_t *message, size_t message_len,
                  const uint8_t signature[114], const uint8_t public_key[57],
                  const uint8_t *context, size_t context_len,
                  const uint8_t phflag, const char *propq)
{
    return ossl_c448_ed448_verify(ctx, signature, public_key, message,
                                  message_len, phflag, context, (uint8_t)context_len,
                                  propq) == C448_SUCCESS;
}

int
ossl_ed448_public_from_private(OSSL_LIB_CTX *ctx, uint8_t out_public_key[57],
                               const uint8_t private_key[57], const char *propq)
{
    return ossl_c448_ed448_derive_public_key(ctx, out_public_key, private_key,
                                             propq) == C448_SUCCESS;
}

Coverage Report

Created: 2025-06-13 06:55

Line	Count	Source (jump to first uncovered line)
1		/*
2		* Copyright 2017-2024 The OpenSSL Project Authors. All Rights Reserved.
3		* Copyright 2015-2016 Cryptography Research, Inc.
4		*
5		* Licensed under the Apache License 2.0 (the "License"). You may not use
6		* this file except in compliance with the License. You can obtain a copy
7		* in the file LICENSE in the source distribution or at
8		* https://www.openssl.org/source/license.html
9		*
10		* Originally written by Mike Hamburg
11		*/
12		#include <string.h>
13		#include <openssl/crypto.h>
14		#include <openssl/evp.h>
15		#include "crypto/ecx.h"
16		#include "curve448_local.h"
17		#include "word.h"
18		#include "ed448.h"
19		#include "internal/numbers.h"
20
21	0	#define COFACTOR 4
22
23		static c448_error_t oneshot_hash(OSSL_LIB_CTX ctx, uint8_t out, size_t outlen,
24		const uint8_t *in, size_t inlen,
25		const char *propq)
26	0	{
27	0	EVP_MD_CTX *hashctx = EVP_MD_CTX_new();
28	0	EVP_MD *shake256 = NULL;
29	0	c448_error_t ret = C448_FAILURE;
30
31	0	if (hashctx == NULL)
32	0	return C448_FAILURE;
33
34	0	shake256 = EVP_MD_fetch(ctx, "SHAKE256", propq);
35	0	if (shake256 == NULL)
36	0	goto err;
37
38	0	if (!EVP_DigestInit_ex(hashctx, shake256, NULL)
39	0	\|\| !EVP_DigestUpdate(hashctx, in, inlen)
40	0	\|\| !EVP_DigestFinalXOF(hashctx, out, outlen))
41	0	goto err;
42
43	0	ret = C448_SUCCESS;
44	0	err:
45	0	EVP_MD_CTX_free(hashctx);
46	0	EVP_MD_free(shake256);
47	0	return ret;
48	0	}
49
50		static void clamp(uint8_t secret_scalar_ser[EDDSA_448_PRIVATE_BYTES])
51	0	{
52	0	secret_scalar_ser[0] &= -COFACTOR;
53	0	secret_scalar_ser[EDDSA_448_PRIVATE_BYTES - 1] = 0;
54	0	secret_scalar_ser[EDDSA_448_PRIVATE_BYTES - 2] \|= 0x80;
55	0	}
56
57		static c448_error_t hash_init_with_dom(OSSL_LIB_CTX ctx, EVP_MD_CTX hashctx,
58		uint8_t prehashed,
59		uint8_t for_prehash,
60		const uint8_t *context,
61		size_t context_len,
62		const char *propq)
63	0	{
64		/* ASCII: "SigEd448", in hex for EBCDIC compatibility */
65	0	const char dom_s[] = "\x53\x69\x67\x45\x64\x34\x34\x38";
66	0	uint8_t dom[2];
67	0	EVP_MD *shake256 = NULL;
68
69	0	if (context_len > UINT8_MAX)
70	0	return C448_FAILURE;
71
72	0	dom[0] = (uint8_t)(2 - (prehashed == 0 ? 1 : 0)
73	0	- (for_prehash == 0 ? 1 : 0));
74	0	dom[1] = (uint8_t)context_len;
75
76	0	shake256 = EVP_MD_fetch(ctx, "SHAKE256", propq);
77	0	if (shake256 == NULL)
78	0	return C448_FAILURE;
79
80	0	if (!EVP_DigestInit_ex(hashctx, shake256, NULL)
81	0	\|\| !EVP_DigestUpdate(hashctx, dom_s, sizeof(dom_s)-1)
82	0	\|\| !EVP_DigestUpdate(hashctx, dom, sizeof(dom))
83	0	\|\| !EVP_DigestUpdate(hashctx, context, context_len)) {
84	0	EVP_MD_free(shake256);
85	0	return C448_FAILURE;
86	0	}
87
88	0	EVP_MD_free(shake256);
89	0	return C448_SUCCESS;
90	0	}
91
92		/* In this file because it uses the hash */
93		c448_error_t
94		ossl_c448_ed448_convert_private_key_to_x448(
95		OSSL_LIB_CTX *ctx,
96		uint8_t x[X448_PRIVATE_BYTES],
97		const uint8_t ed [EDDSA_448_PRIVATE_BYTES],
98		const char *propq)
99	0	{
100		/* pass the private key through oneshot_hash function */
101		/* and keep the first X448_PRIVATE_BYTES bytes */
102	0	return oneshot_hash(ctx, x, X448_PRIVATE_BYTES, ed,
103	0	EDDSA_448_PRIVATE_BYTES, propq);
104	0	}
105
106		c448_error_t
107		ossl_c448_ed448_derive_public_key(
108		OSSL_LIB_CTX *ctx,
109		uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
110		const uint8_t privkey[EDDSA_448_PRIVATE_BYTES],
111		const char *propq)
112	0	{
113		/* only this much used for keygen */
114	0	uint8_t secret_scalar_ser[EDDSA_448_PRIVATE_BYTES];
115	0	curve448_scalar_t secret_scalar;
116	0	unsigned int c;
117	0	curve448_point_t p;
118
119	0	if (!oneshot_hash(ctx, secret_scalar_ser, sizeof(secret_scalar_ser),
120	0	privkey,
121	0	EDDSA_448_PRIVATE_BYTES,
122	0	propq))
123	0	return C448_FAILURE;
124
125	0	clamp(secret_scalar_ser);
126
127	0	ossl_curve448_scalar_decode_long(secret_scalar, secret_scalar_ser,
128	0	sizeof(secret_scalar_ser));
129
130		/*
131		* Since we are going to mul_by_cofactor during encoding, divide by it
132		* here. However, the EdDSA base point is not the same as the decaf base
133		* point if the sigma isogeny is in use: the EdDSA base point is on
134		* Etwist_d/(1-d) and the decaf base point is on Etwist_d, and when
135		* converted it effectively picks up a factor of 2 from the isogenies. So
136		* we might start at 2 instead of 1.
137		*/
138	0	for (c = 1; c < C448_EDDSA_ENCODE_RATIO; c <<= 1)
139	0	ossl_curve448_scalar_halve(secret_scalar, secret_scalar);
140
141	0	ossl_curve448_precomputed_scalarmul(p, ossl_curve448_precomputed_base,
142	0	secret_scalar);
143
144	0	ossl_curve448_point_mul_by_ratio_and_encode_like_eddsa(pubkey, p);
145
146		/* Cleanup */
147	0	ossl_curve448_scalar_destroy(secret_scalar);
148	0	ossl_curve448_point_destroy(p);
149	0	OPENSSL_cleanse(secret_scalar_ser, sizeof(secret_scalar_ser));
150
151	0	return C448_SUCCESS;
152	0	}
153
154		c448_error_t
155		ossl_c448_ed448_sign(OSSL_LIB_CTX *ctx,
156		uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
157		const uint8_t privkey[EDDSA_448_PRIVATE_BYTES],
158		const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
159		const uint8_t *message, size_t message_len,
160		uint8_t prehashed, const uint8_t *context,
161		size_t context_len, const char *propq)
162	0	{
163	0	curve448_scalar_t secret_scalar;
164	0	EVP_MD_CTX *hashctx = EVP_MD_CTX_new();
165	0	c448_error_t ret = C448_FAILURE;
166	0	curve448_scalar_t nonce_scalar;
167	0	uint8_t nonce_point[EDDSA_448_PUBLIC_BYTES] = { 0 };
168	0	unsigned int c;
169	0	curve448_scalar_t challenge_scalar;
170
171	0	if (hashctx == NULL)
172	0	return C448_FAILURE;
173
174	0	{
175		/*
176		* Schedule the secret key, First EDDSA_448_PRIVATE_BYTES is serialized
177		* secret scalar,next EDDSA_448_PRIVATE_BYTES bytes is the seed.
178		*/
179	0	uint8_t expanded[EDDSA_448_PRIVATE_BYTES * 2];
180
181	0	if (!oneshot_hash(ctx, expanded, sizeof(expanded), privkey,
182	0	EDDSA_448_PRIVATE_BYTES, propq))
183	0	goto err;
184	0	clamp(expanded);
185	0	ossl_curve448_scalar_decode_long(secret_scalar, expanded,
186	0	EDDSA_448_PRIVATE_BYTES);
187
188		/* Hash to create the nonce */
189	0	if (!hash_init_with_dom(ctx, hashctx, prehashed, 0, context,
190	0	context_len, propq)
191	0	\|\| !EVP_DigestUpdate(hashctx,
192	0	expanded + EDDSA_448_PRIVATE_BYTES,
193	0	EDDSA_448_PRIVATE_BYTES)
194	0	\|\| !EVP_DigestUpdate(hashctx, message, message_len)) {
195	0	OPENSSL_cleanse(expanded, sizeof(expanded));
196	0	goto err;
197	0	}
198	0	OPENSSL_cleanse(expanded, sizeof(expanded));
199	0	}
200
201		/* Decode the nonce */
202	0	{
203	0	uint8_t nonce[2 * EDDSA_448_PRIVATE_BYTES];
204
205	0	if (!EVP_DigestFinalXOF(hashctx, nonce, sizeof(nonce)))
206	0	goto err;
207	0	ossl_curve448_scalar_decode_long(nonce_scalar, nonce, sizeof(nonce));
208	0	OPENSSL_cleanse(nonce, sizeof(nonce));
209	0	}
210
211	0	{
212		/* Scalarmul to create the nonce-point */
213	0	curve448_scalar_t nonce_scalar_2;
214	0	curve448_point_t p;
215
216	0	ossl_curve448_scalar_halve(nonce_scalar_2, nonce_scalar);
217	0	for (c = 2; c < C448_EDDSA_ENCODE_RATIO; c <<= 1)
218	0	ossl_curve448_scalar_halve(nonce_scalar_2, nonce_scalar_2);
219
220	0	ossl_curve448_precomputed_scalarmul(p, ossl_curve448_precomputed_base,
221	0	nonce_scalar_2);
222	0	ossl_curve448_point_mul_by_ratio_and_encode_like_eddsa(nonce_point, p);
223	0	ossl_curve448_point_destroy(p);
224	0	ossl_curve448_scalar_destroy(nonce_scalar_2);
225	0	}
226
227	0	{
228	0	uint8_t challenge[2 * EDDSA_448_PRIVATE_BYTES];
229
230		/* Compute the challenge */
231	0	if (!hash_init_with_dom(ctx, hashctx, prehashed, 0, context, context_len,
232	0	propq)
233	0	\|\| !EVP_DigestUpdate(hashctx, nonce_point, sizeof(nonce_point))
234	0	\|\| !EVP_DigestUpdate(hashctx, pubkey, EDDSA_448_PUBLIC_BYTES)
235	0	\|\| !EVP_DigestUpdate(hashctx, message, message_len)
236	0	\|\| !EVP_DigestFinalXOF(hashctx, challenge, sizeof(challenge)))
237	0	goto err;
238
239	0	ossl_curve448_scalar_decode_long(challenge_scalar, challenge,
240	0	sizeof(challenge));
241	0	OPENSSL_cleanse(challenge, sizeof(challenge));
242	0	}
243
244	0	ossl_curve448_scalar_mul(challenge_scalar, challenge_scalar, secret_scalar);
245	0	ossl_curve448_scalar_add(challenge_scalar, challenge_scalar, nonce_scalar);
246
247	0	OPENSSL_cleanse(signature, EDDSA_448_SIGNATURE_BYTES);
248	0	memcpy(signature, nonce_point, sizeof(nonce_point));
249	0	ossl_curve448_scalar_encode(&signature[EDDSA_448_PUBLIC_BYTES],
250	0	challenge_scalar);
251
252	0	ossl_curve448_scalar_destroy(secret_scalar);
253	0	ossl_curve448_scalar_destroy(nonce_scalar);
254	0	ossl_curve448_scalar_destroy(challenge_scalar);
255
256	0	ret = C448_SUCCESS;
257	0	err:
258	0	EVP_MD_CTX_free(hashctx);
259	0	return ret;
260	0	}
261
262		c448_error_t
263		ossl_c448_ed448_sign_prehash(
264		OSSL_LIB_CTX *ctx,
265		uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
266		const uint8_t privkey[EDDSA_448_PRIVATE_BYTES],
267		const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
268		const uint8_t hash[64], const uint8_t *context,
269		size_t context_len, const char *propq)
270	0	{
271	0	return ossl_c448_ed448_sign(ctx, signature, privkey, pubkey, hash, 64, 1,
272	0	context, context_len, propq);
273	0	}
274
275		static c448_error_t
276		c448_ed448_pubkey_verify(const uint8_t *pub, size_t pub_len)
277	0	{
278	0	curve448_point_t pk_point;
279
280	0	if (pub_len != EDDSA_448_PUBLIC_BYTES)
281	0	return C448_FAILURE;
282
283	0	return ossl_curve448_point_decode_like_eddsa_and_mul_by_ratio(pk_point, pub);
284	0	}
285
286		c448_error_t
287		ossl_c448_ed448_verify(
288		OSSL_LIB_CTX *ctx,
289		const uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
290		const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
291		const uint8_t *message, size_t message_len,
292		uint8_t prehashed, const uint8_t *context,
293		uint8_t context_len, const char *propq)
294	0	{
295	0	curve448_point_t pk_point, r_point;
296	0	c448_error_t error;
297	0	curve448_scalar_t challenge_scalar;
298	0	curve448_scalar_t response_scalar;
299		/* Order in little endian format */
300	0	static const uint8_t order[] = {
301	0	0xF3, 0x44, 0x58, 0xAB, 0x92, 0xC2, 0x78, 0x23, 0x55, 0x8F, 0xC5, 0x8D,
302	0	0x72, 0xC2, 0x6C, 0x21, 0x90, 0x36, 0xD6, 0xAE, 0x49, 0xDB, 0x4E, 0xC4,
303	0	0xE9, 0x23, 0xCA, 0x7C, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
304	0	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
305	0	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x3F, 0x00
306	0	};
307	0	int i;
308
309		/*
310		* Check that s (second 57 bytes of the sig) is less than the order. Both
311		* s and the order are in little-endian format. This can be done in
312		* variable time, since if this is not the case the signature if publicly
313		* invalid.
314		*/
315	0	for (i = EDDSA_448_PUBLIC_BYTES - 1; i >= 0; i--) {
316	0	if (signature[i + EDDSA_448_PUBLIC_BYTES] > order[i])
317	0	return C448_FAILURE;
318	0	if (signature[i + EDDSA_448_PUBLIC_BYTES] < order[i])
319	0	break;
320	0	}
321	0	if (i < 0)
322	0	return C448_FAILURE;
323
324	0	error =
325	0	ossl_curve448_point_decode_like_eddsa_and_mul_by_ratio(pk_point, pubkey);
326
327	0	if (C448_SUCCESS != error)
328	0	return error;
329
330	0	error =
331	0	ossl_curve448_point_decode_like_eddsa_and_mul_by_ratio(r_point, signature);
332	0	if (C448_SUCCESS != error)
333	0	return error;
334
335	0	{
336		/* Compute the challenge */
337	0	EVP_MD_CTX *hashctx = EVP_MD_CTX_new();
338	0	uint8_t challenge[2 * EDDSA_448_PRIVATE_BYTES];
339
340	0	if (hashctx == NULL
341	0	\|\| !hash_init_with_dom(ctx, hashctx, prehashed, 0, context,
342	0	context_len, propq)
343	0	\|\| !EVP_DigestUpdate(hashctx, signature, EDDSA_448_PUBLIC_BYTES)
344	0	\|\| !EVP_DigestUpdate(hashctx, pubkey, EDDSA_448_PUBLIC_BYTES)
345	0	\|\| !EVP_DigestUpdate(hashctx, message, message_len)
346	0	\|\| !EVP_DigestFinalXOF(hashctx, challenge, sizeof(challenge))) {
347	0	EVP_MD_CTX_free(hashctx);
348	0	return C448_FAILURE;
349	0	}
350
351	0	EVP_MD_CTX_free(hashctx);
352	0	ossl_curve448_scalar_decode_long(challenge_scalar, challenge,
353	0	sizeof(challenge));
354	0	OPENSSL_cleanse(challenge, sizeof(challenge));
355	0	}
356	0	ossl_curve448_scalar_sub(challenge_scalar, ossl_curve448_scalar_zero,
357	0	challenge_scalar);
358
359	0	ossl_curve448_scalar_decode_long(response_scalar,
360	0	&signature[EDDSA_448_PUBLIC_BYTES],
361	0	EDDSA_448_PRIVATE_BYTES);
362
363		/* pk_point = -c(x(P)) + (cx + k)G = kG */
364	0	ossl_curve448_base_double_scalarmul_non_secret(pk_point,
365	0	response_scalar,
366	0	pk_point, challenge_scalar);
367	0	return c448_succeed_if(ossl_curve448_point_eq(pk_point, r_point));
368	0	}
369
370		c448_error_t
371		ossl_c448_ed448_verify_prehash(
372		OSSL_LIB_CTX *ctx,
373		const uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
374		const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
375		const uint8_t hash[64], const uint8_t *context,
376		uint8_t context_len, const char *propq)
377	0	{
378	0	return ossl_c448_ed448_verify(ctx, signature, pubkey, hash, 64, 1, context,
379	0	context_len, propq);
380	0	}
381
382		int
383		ossl_ed448_sign(OSSL_LIB_CTX ctx, uint8_t out_sig,
384		const uint8_t *message, size_t message_len,
385		const uint8_t public_key[57], const uint8_t private_key[57],
386		const uint8_t *context, size_t context_len,
387		const uint8_t phflag, const char *propq)
388	0	{
389	0	return ossl_c448_ed448_sign(ctx, out_sig, private_key, public_key, message,
390	0	message_len, phflag, context, context_len,
391	0	propq) == C448_SUCCESS;
392	0	}
393
394		/*
395		* This function should not be necessary since ossl_ed448_verify() already
396		* does this check internally.
397		* For some reason the FIPS ACVP requires a EDDSA KeyVer test.
398		*/
399		int
400		ossl_ed448_pubkey_verify(const uint8_t *pub, size_t pub_len)
401	0	{
402	0	return c448_ed448_pubkey_verify(pub, pub_len);
403	0	}
404
405		int
406		ossl_ed448_verify(OSSL_LIB_CTX *ctx,
407		const uint8_t *message, size_t message_len,
408		const uint8_t signature[114], const uint8_t public_key[57],
409		const uint8_t *context, size_t context_len,
410		const uint8_t phflag, const char *propq)
411	0	{
412	0	return ossl_c448_ed448_verify(ctx, signature, public_key, message,
413	0	message_len, phflag, context, (uint8_t)context_len,
414	0	propq) == C448_SUCCESS;
415	0	}
416
417		int
418		ossl_ed448_public_from_private(OSSL_LIB_CTX *ctx, uint8_t out_public_key[57],
419		const uint8_t private_key[57], const char *propq)
420	0	{
421	0	return ossl_c448_ed448_derive_public_key(ctx, out_public_key, private_key,
422	0	propq) == C448_SUCCESS;
423	0	}